Value of cranial nerve involvement found on MRI in staging of nasopharyngeal carcinoma

Abstract

Objective To identify the value of cranial nerve involvement found on magnetic resonance imaging (MRI) in staging of nasopharyngeal carcinoma (NPC).Methods A retrospective analysis was performed on the clinical data of 816 patients with NPC initially diagnosed by MRI during 2005 -2007.The patients with stage T4 NPC were divided into cranial nerve subgroup,which was defined as patients who had cranial nerve involvement on MRI,but without cranial nerve palsy or other T4-related anatomical structure involvement,and other subgroup,which was defined as other patients with stage T4 NPC ;the patients with stage Ⅳ a NPC were divided into cranial nerve subgroup,which was defined as patients with T4N0-2 NPC who were classified into the cranial nerve subgroup of patients with stage T4 NPC,and other subgroup,which was defined as other patients with stage Ⅳa NPC.The survivals of the subgroups were compared.The Kaplan-Meier method was used for calculating survival rates,and the survival differences were analyzed by the log-rank test.Results The follow-up rate was 94.1％.Cranial nerve involvement was seen in 38.5％ of all patients.Local recurrence-free survival,distant metastasis-free survival,and disease-related survival curves of patients with stage T2 and T3 NPC and the cranial nerve subgroup of patients with stage T4 NPC coincided,but they were separated from the curves of the other subgroup of patients with stage T4 NPC.There was no significant difference in 5-year disease-related survival rate between the cranial nerve subgroup of patients with stage Ⅳa NPC and the patients with stage Ⅲ NPC (x2 =0.18,P =0.674),but significant differences were found when this subgroup was compared with patients with stage Ⅱ NPC (x2 =5.86,P =0.015) and the other subgroup of patients with stage Ⅳa NPC (x2 =7.23,P =0.007).Conclusions The patients with stage T4/Ⅳa NPC who have cranial nerve involvement on MRI,but without other T4-related anatomical structure involvement,have similar local recurrence-free survival rate and distant metastasis-free survival rate as those with stage T2 and T3 NPC and have a similar disease-related survival rate as those with stage Ⅲ NPC,and their prognosis is better than that of the other subgroup of patients with stage T4/Ⅳa NPC.It may lead to overtreatment for patients if they are classified as stage T4/Ⅳa and receive the treatment regimen for stage Ⅳ NPC. Key words: Nasopharyngeal neoplasms/radiotherapy; Magnetic resonance imaging; Neoplasm staging